The invention generally relates to a slimhole fluid tester.
For purposes of producing a well fluid (methane, for example) from one or more subterranean formations, the formation(s) may be drilled to create a well bore that extends through the formations(s). The well bore may be cased with a steel casing.
It is common for the well bore to pass through several regions, or zones, of the well, each of which contains a particular well fluid. As an example, some zones may contain carbon dioxide, some zones may contain hydrogen sulfide and some zones may contain methane. Therefore, to produce methane, for example, it is desirable to produce from the zones that primarily contain methane and avoid producing from the zones that primarily contain hydrogen sulfide and carbon dioxide, as examples. In this manner, once production begins, the zones may be isolated by packers so that primarily the desired well fluid is produced.
Before production begins, however, a perforating gun typically is lowered downhole to pierce the well casing and form perforation tunnels in the formation(s) at various sites along the wellbore for purposes of enhancing and/or allowing the production of well fluids from the formation. In this manner, typically, the perforating gun is part of a perforating gun string, an assembly that may include several perforating guns that are located at different depths. The perforating gun string typically is positioned downhole via a wireline or coiled tubing (as examples) until the perforating gun string is at the desired depth. The perforating guns are then fired to perforate the formation(s) at several sites.
After perforation, the well may then be tested to determine the composition of the well fluids that are associated with the various zones of the well. In this manner, a testing tool, or tester, may be lowered downhole to test the different zones of the well. The tester typically includes packers to seal off and thus, isolate the different zones so that well fluids from the different zones may be sampled by the tester.
However, before the packers are set to isolate the different zones, the fluids from the different zones may intermingle, and thus, once the packers of the tester are set, a particular sealed zone may initially contain a mixture of fluids from other zones. Therefore, to obtain an accurate sample of the fluid in a particular zone, the tester may include a pump to remove fluid from the particular zone before the sample is taken. This removal of fluid ideally flushes the intermingling fluids from the zone, leaving the fluid produced by the zone being tested. However, for a well bore that has a small diameter (a diameter of approximately 2xe2x85x9e inches, as an example), otherwise known as a slimhole, the pump may be too large to be used in the well bore.
Thus, there is a continuing need for an arrangement that addresses one or more of the problems that are stated above.
In an embodiment of the invention, a tool that is usable in a subterranean well to sample well fluid from a zone does not include a pump to remove well fluid from the zone for purposes of sampling. Instead, the tool includes a flow path that is in communication with the zone and a region of the well above the zone to use a pressure differential created or naturally occurring between the zone and the region of the well above the zone to flow well fluid from the zone. The tool may also include a flow path that is in communication with the region of the well above the zone and the region of the well below the zone to equalize pressure along the tool and thereby prevent unintended axial movement of the tool. A fluid sampler of the tool samples a composition of the well fluid from the zone.
Advantages and other features of the invention will become apparent from the following description, drawing and claims.